The number of commercially-available therapeutic proteins has increased dramatically in recent years and most of these proteins are glycoproteins. The presence of sialic acid in a glycoprotein can positively affect absorption, serum half-life, and clearance from the serum, as well as the physical, chemical and immunogenic properties of the respective glycoprotein. In certain circumstances, it may therefore be desirable to increase the sialic acid content of a glycoprotein intended for use in pharmacologic applications.